The legislation also bans magazines holding more than 10 rounds of ammunition and requires people who already own assault rifles to use secure storage and safety devices and bars them from selling high-capacity clips.

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“No weapon is taken from anyone,” said Feinstein. “The purpose is to dry up the supply of these weapons over time.”

Unlike the 1994 assault-weapons ban, there is no sunset provision in Feinstein’s newest gun-control bill.

The lawmakers introduced the bill at a press conference with law-enforcement groups supporting the legislation. Groups endorsing the bill include the U.S. Conference of Mayors, the Major Cities Chiefs Association, the Police Foundation, and the International Association of Campus Law Enforcement Administrators.

Feinstein acknowledged the bill would face stiff opposition in Congress.

“Getting this bill signed into law will be an uphill battle, and I recognize that — but it’s a battle worth having,” she said. “We must balance the desire of a few to own military-style assault weapons with the growing threat to lives across America.”

The bill would ban the sale, transfer, manufacture and import of all semi-automatic rifles and pistols that can accept detachable magazines and have at least one military feature.

It would also ban semi-automatic rifles and handguns that have fixed magazines capable of carrying more than 10 rounds and all semi-automatic shotguns that have folding or detachable stocks, pistol grips, forward grips, or fixed magazines with room for more than five rounds.

It includes a grandfather clause that would exempt assault weapons "lawfully possessed" on the date of enactment. Background checks would be required prior to the sale or transfer of weapons exempted under the clause.

The National Rifle Association (NRA) slammed the effort, signaling it will launch an all-out lobbying effort to defeat it.

“Sen. Feinstein has been trying to ban guns from law-abiding citizens for decades,” the NRA said in a statement. “It's disappointing but not surprising that she is once again focused on curtailing the Constitution instead of prosecuting criminals or fixing our broken mental health system.

“The American people know gun bans do not work and we are confident Congress will reject Senator Feinstein's wrong-headed approach,” the group added.

Feinstein said she designed the bill to make it more difficult for gun manufacturers to evade restrictions by altering just one or a few features. The 1994 federal assault-weapons ban, which Feinstein also sponsored, was widely criticized as ineffective because of various loopholes.

Feinstein emphasized that her bill exempts more than 2,200 hunting and sports rifles or any gun manually operated by bolt, lever or slide action. It also exempts weapons used by active and retired law enforcement officials.

Feinstein argues the 1994 ban was effective, citing a Justice Department study that found it led to a 6.7-percent decrease in gun murders. She also pointed to a finding from the Police Executive Research Forum that nearly 40 percent of police departments reported an increase in criminal use of assault weapons since the ban expired in 2004.